304 poisons: their effects and detection. [§§364,365, 
§ 364. Physiological Action. —From experiments on animals, the 
essential action of morphine on the nervous and arterial systems has in 
some measure been examined. There is no very considerable action on 
the heart. The beats are first accelerated, then diminished in frequency ; 
but very large doses introduced directly into the circulation at once 
diminish the pulsations, and no acceleration is noticed. The slowing 
may go on to heart-paralysis. The slowing is central in its origin, for 
on the vagi being cut, morphine always quickens. With regard to the 
peripheric ends of the vagi, small doses excite, large paralyse. If all 
the nerves going to the heart are divided, there is first a considerable 
acceleration, and then a slowing and weakening of the pulsation. The 
arterial blood-pressure, at first increased, is afterwards diminished. 
This increase of blood-pressure is noticed during the acceleration of 
the pulse, and also during some portion of the time during which the 
pulse is slowed. Stockman and D. B. Dott, 1 experimenting on rabbits 
and frogs, consider that a medium dose of morphine first of all depresses 
the spinal cord and then excites it, for tetanus follows. If morphine is in 
sufficient quantity thrown into the circulation, then tetanus at once 
occurs. It would thus appear that depression and stimulation are entirely 
a matter of dosage. Gescheidlen, in his researches on the frog, found 
the motor nerves at first excited, and then depressed. When the 
doses were large, there was scarcely any excitement, but the reverse 
effect, in the neighbourhood of the place of application. According to 
other observers, the function of the motor nerves may be annihilated. 2 
According to Meihuizen, reflex action, at first much diminished, is later, 
after several hours, normal, and later still again increased. The 
intestinal movements are transitorily increased. In the dog there has 
been noticed a greater flow of saliva than usual, and the flow of bile 
from the gall-bladder is diminished. The pupils in animals are mostly 
contracted, but, if convulsions occur towards death, they are dilated. 
§ 365. Physiological Effect of Morphine Derivatives. —By intro¬ 
ducing methyl, or amyl, or ethyl, into the morphine molecule, the 
narcotic action is diminished, while the tetanic effects are increased. 
Acetyl, diacetyl, benzoyl, and dibenzoyl morphine, morphine sulphuric 
ether, and nitrosomorphine are all weaker narcotics than morphine, but, 
on the other hand, they depress the functions of the spinal cord and bring 
on, in large doses, tetanus. 
The introduction of two methyl groups into morphine, as in metho- 
codeine, C 17 H 17 MeNO(OH)—Me, entirely alters the physiological effect. 
This compound has an action on voluntary muscle causing gradual 
paralysis. 
The chlorine derivatives, trichlormorphine and chlorcodeine, have 
the characteristic action of the morphine group on the central nervous 
1 Brit. Med. Journ. (2), 1890, 189-192. 2 Arch. J. d. Ges. Physiol ., vii. 201. 
